1. Technical Field
The present invention relates to an optical device and an image display apparatus.
2. Related Art
A projector, a head-mounted display, and other apparatus are used as an image display apparatus that includes an image forming device having two-dimensionally arranged pixels, produces an image by controlling the wavelength, the intensity, and other factors of light on a pixel basis in the image forming device, and enlarges and displays the image through a lens or any other optical system. A liquid crystal device and an organic EL device are, for example, used as the image forming device, and these devices have been improved in terms of resolution year after year.
At present, in the image display apparatus market, products having very high resolution or what is called full-high-vision resolution are widely used. It is expected that the current image display apparatus transitions in the future to products having still higher resolution called, for example, 4K and 8K (super-high-vision resolution).
Among methods for achieving such high-resolution display, there is a method using a pixel shifter that shifts the position where an image produced by an image forming device is projected. An example of the pixel shifter uses refraction (light modulation) in an optical element to shift the optical path. The optical element is configured to be rotatable around an axis, and the rotation of the optical element causes light passing therethrough to be refracted, resulting in a shift of the optical path. Further, in this process, the amount of shift can be adjusted in accordance with the amount of rotation.
In the pixel shifter described above, which shifts the optical path based on the rotation of the optical element, an unnecessary vibration component other than the rotation of the optical element that shifts the optical path (such as residual vibration produced when the optical element stops rotating or when the direction of the rotation changes) makes the optical path unstable, resulting in a decrease in quality of a displayed image.
JP-A-2011-158589 discloses an optical path control apparatus (pixel shifter) that shifts the optical path based on rotation of an optical element and also discloses that vibration other than the rotation of the optical element is suppressed. The optical path control apparatus described in JP-A-2011-158589 has, however, a problem of a complicated control circuit because unnecessary vibration is suppressed based on drive control of the rotation of the optical element.